Def. 1-
(noun) a liquid or semi-liquid edible dressing or condiment served as an accompaniment to or an ingredient in a meat, dessert, or other food: pizza sauce, steak sauce, cranberry sauce, chocolate sauce, etc., or (verb) to add said sauce to something.

Def 2-
(noun) an intoxicating substance, usually hard liquor.

Def 3-
(noun) A word used to describe something as especially good, often used stand alone as an interjection.

Def 4-
(interrogative) slang for "source"- usually used when asking for the source a particular file on a "chan" or other chat/image board.

Def 5-
(archaic- now usually only heard in old Tom & Jerry or Bugs Bunny cartoon reruns from the '40s) rude or impudent speech, especially applying to "backtalk."

Def 1-
"This pasta needs more marinara sauce."

Def 2-
"I threw back way too much of the sauce last night- I can't remember getting this new tattoo."